Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Identification of solid N2O in interstellar ices using open JWST data

V. Karteyeva, R. Nakibov, I. Petrashkevich, M. Medvedev, A. Vasyunin

TL;DR

JWST enables secure identification of solid N2O in interstellar ices by combining open spectra with laboratory ice analogues. The study surveys 50 protostars to locate the NN-stretch feature in apolar CO/CO2/N2-rich mantles and to constrain the solid N2O abundance relative to CO. The authors report secure identifications in 16 protostars, show that N2O resides mainly in apolar ice layers, and provide band strengths for apolar mixtures, along with a tentative HNCO CN-stretch assignment in a crowded 4.4 μm region. These results constrain nitrogen chemistry in icy mantles and inform irradiation-driven formation pathways of nitrogen-bearing species with potential links to prebiotic chemistry.

Abstract

Context. There are only six molecules containing N-O bond that are detected in gaseous phase in interstellar medium. One of those is nitrous oxide (N2O), which was searched for but not found in solid form from as early as Infrared Space Observatory (ISO) mission was launched. The observational capabilities of James Webb Space Telescope (JWST) present a possibility to identify solid interstellar N2O. Aims. We aim to identify nitrous oxide in open JWST spectra of interstellar ices towards a sample of Class 0, 0/I and flat protostars using the relevant laboratory mixtures of N2O-bearing interstellar ice analogues. Methods. A set of laboratory infrared transmission spectra was obtained for the following mixtures: N2O:CO2=1:20, N2O:CO=1:20, N2O:N2=1:20, N2O:CO2:CO=1:15:5, N2O:CO2:N2=1:15:13 at 10-23 K. A search for N2O in JWST NIRSpec spectra towards 50 protostars was performed by fitting the 4.44-4.47 um (2250-2235 cm-1) NN-stretch absorption band with new laboratory mixtures of N2O-bearing ices. Results. We claim the first secure identification of N2O in 16 protostars. The fitting results show that N2O is formed predominantly within the apolar layer of the ice mantles, rich in CO, CO2 and N2. The abundance of solid N2O is estimated as 0.2-2.1% relative to solid CO. We present band strengths for N2O in the mixtures corresponding to the apolar layer. Also, an identification of the C-N stretch band at 4.42 um (2260 cm-1) is reported, which we tentatively assign to HNCO, the simplest C-N bond carrier.

Identification of solid N2O in interstellar ices using open JWST data

TL;DR

JWST enables secure identification of solid N2O in interstellar ices by combining open spectra with laboratory ice analogues. The study surveys 50 protostars to locate the NN-stretch feature in apolar CO/CO2/N2-rich mantles and to constrain the solid N2O abundance relative to CO. The authors report secure identifications in 16 protostars, show that N2O resides mainly in apolar ice layers, and provide band strengths for apolar mixtures, along with a tentative HNCO CN-stretch assignment in a crowded 4.4 μm region. These results constrain nitrogen chemistry in icy mantles and inform irradiation-driven formation pathways of nitrogen-bearing species with potential links to prebiotic chemistry.

Abstract

Context. There are only six molecules containing N-O bond that are detected in gaseous phase in interstellar medium. One of those is nitrous oxide (N2O), which was searched for but not found in solid form from as early as Infrared Space Observatory (ISO) mission was launched. The observational capabilities of James Webb Space Telescope (JWST) present a possibility to identify solid interstellar N2O. Aims. We aim to identify nitrous oxide in open JWST spectra of interstellar ices towards a sample of Class 0, 0/I and flat protostars using the relevant laboratory mixtures of N2O-bearing interstellar ice analogues. Methods. A set of laboratory infrared transmission spectra was obtained for the following mixtures: N2O:CO2=1:20, N2O:CO=1:20, N2O:N2=1:20, N2O:CO2:CO=1:15:5, N2O:CO2:N2=1:15:13 at 10-23 K. A search for N2O in JWST NIRSpec spectra towards 50 protostars was performed by fitting the 4.44-4.47 um (2250-2235 cm-1) NN-stretch absorption band with new laboratory mixtures of N2O-bearing ices. Results. We claim the first secure identification of N2O in 16 protostars. The fitting results show that N2O is formed predominantly within the apolar layer of the ice mantles, rich in CO, CO2 and N2. The abundance of solid N2O is estimated as 0.2-2.1% relative to solid CO. We present band strengths for N2O in the mixtures corresponding to the apolar layer. Also, an identification of the C-N stretch band at 4.42 um (2260 cm-1) is reported, which we tentatively assign to HNCO, the simplest C-N bond carrier.
Paper Structure (8 sections, 1 equation, 4 figures, 2 tables)

This paper contains 8 sections, 1 equation, 4 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Experimental setup and methods
  3. Observations and fitting procedure
  4. Results and Discussion
  5. Apertures
  6. Baselines
  7. Sources and column densities
  8. Fitting results

Figures (4)

  • Figure 1: The $\nu_3$ mode of N$_2$O in pure N$_2$O, N$_2$O:H$_2$O=1:20 and nitrous oxide in astrochemically relevant matrices corresponding to the apolar layer of ice mantles N$_2$O:CO=1:20, N$_2$O:N$_2$=1:20, N$_2$O:CO$_2$:N$_2$=1:15:13, N$_2$O:CO$_2$:CO=1:15:5, N$_2$O:CO$_2$=1:20. Spectra are displayed only for the lowest and the highest temperatures considered in this study.
  • Figure 2: Intensity maps at 4.4 $\mu$m with the apertures chosen for the fit. Aperture centers and diameters are listed in Table \ref{['tab:table_sources']}.
  • Figure 3: Raw and processed observational spectra with fitted polynomial continuum. Anchor points are represented with red dots, fitted continuum with red line. Original and processed observational spectra are shown with orange and black lines, respectively.
  • Figure 4: Observational data at 4.45 $\mu$m, fitted curves and Gaussian function for HNCO. Black line represents the observational spectra, dashed --- laboratory spectra of N$_2$O in apolar environment, short dashed --- HNCO Gaussian, green --- combined N$_2$O feature, and red --- full fitted curve.